1. Field of the Invention
The present invention relates to a system for providing support so that a pilot operating an aircraft can perform a flight that reduces noise pollution in areas where noise is especially likely to be a problem, such as hospitals, schools, residential areas, this support being provided by displaying the noise conditions on the ground to this pilot.
2. Description of the Related Art
Aircraft perform flight operations while generating noise. This noise is generated from various types of sound sources such as the engine, propellers (rotors in the case of helicopters), landing gear and the like. Furthermore, while noise generated by aircraft is being propagated through the atmosphere so that this noise reaches the ground, the noise is affected by environmental conditions at the location in question such as the wind direction, wind velocity, humidity and density of the atmosphere and the like since phenomena such as attenuation, diffraction and the like occur as a result of such atmospheric conditions. For such reasons, the noise heard by the pilot inside the aircraft does not always coincide with the actual noise conditions on the ground.
Furthermore, countermeasures against noise on the ground must be performed not only in accordance with the absolute magnitude of the noise, but also in accordance with the conditions of utilization of the region in question. For example, even noise levels that are not a problem in the case of rivers, lakes and marshes, forest areas, industrial areas and the like are currently recognized as severe noise pollution in the case of hospitals, schools, densely populated areas an the like. In cases where the pilot is flying over familiar territory, the pilot can avoid places where noise pollution is a problem; however, in the case of areas that are being overflown for the first time, it is difficult for the pilot to obtain a sufficient grasp of the conditions in these areas.
Generally, a method is used in which the noise that is generated by noise generating sources is determined either experimentally or theoretically, and the conditions of this noise are evaluated by drawing contours so that these contours are superimposed on a map of the surrounding area. However, conventional techniques are intended for use in a desktop investigation that is performed offline; it is not an object of such techniques to perform a display in real time, and to reflect the results of this display in the operation and control of noise generating sources. In particular, a device which is mounted in aircraft, and which supports the reduction of noise pollution by displaying such information to the pilot has not yet been realized.
A “low-noise flight support device for helicopters” is disclosed in Japanese Unexamined Patent Application No. 6-206594 (title of the invention: “LOW-NOISE FLIGHT SUPPORT DEVICE FOR HELICOPTERS”, disclosed on Jul. 26, 1994) as a technique for reducing the noise generated by helicopters. This invention aims at providing a flight support device which realizes a rate of descent that minimizes the blade slapping sound that is generated by the flight of the helicopter. In concrete terms, this system comprises means for detecting the air speed of the helicopter, means for detecting the rate of descent, a low-noise advance path computer and a display device; in this system, the abovementioned low-noise advance path computer inputs the output from the air speed detection means and the output from the descent rate detection means, outputs a signal indicating the noise level on the ground caused by the helicopter to the display device on the basis of correlation data with an internally stored noise level, and also outputs (to the display device) a signal indicating designated correction values for the rate of descent and air speed that are to be adopted in order to reduce noise to the display device. This is a device which supports the performance of a flight by the pilot so that the blade slapping noise generated by the helicopter is reduced, and is not a device that considers noise conditions on the ground.
Furthermore, a “flight map display device” whose object is to realize a flight map display device that can increase the display speed by drawing a compass rose so that the top of the display screen coincides with a reference bearing, and then rotating and displaying this compass rose in accordance with information relating to the aircraft, has been proposed in Japanese Unexamined Patent Application No. 2002-31543 (title of the invention: “FLIGHT MAP DISPLAY DEVICE”, disclosed on Jan. 31, 2002). This flight map display device is a flight map display device which is mounted in an aircraft, and which displays a map of the flight area and a compass rose that indicates a reference bearing on a display screen, wherein this device comprises a graphic drawing part which draws the compass rose described above so that the top of the display screen coincides with the reference direction described above, and a rotating part which rotates the compass rose drawn by the graphics drawing part so that the bearing of the aircraft detected on the outside coincides with the top of the display screen, and this device is devised so that the output of a rotation calculating part is displayed on the screen. Although this invention displays a map of the flight area, this is not a device that supports the pilot in performing a flight that takes conditions of the noise on the ground into account and reduces noise.
In addition, a research paper relating to a method for estimating the noise of a helicopter on the ground on the basis of measured data is introduced in “A New Technique for Estimating Ground Footprint Acoustics for Rotorcraft Using Measured Sound Fields” (Mark R. Wilson, Arnold W. Mueller, and Charles K. Rutledge, presented at the American Helicopter Society Vertical Lift Conference, San Francisco, Calif., 1995), a research paper relating to a method for setting a low-noise flight system and evaluating noise in the surrounding area is introduced in “A Tool for Low Noise Procedures Design and Community Noise Impact Assessment: The Rotorcraft Noise Mode (RNM)”, David A. Conner and Juliet A. Page, presented at HeliJapan 2002, Tochigi, Japan, 2002), and a research paper relating to the ground surface attenuation of aircraft noise is introduced in “Prediction Method of Lateral Attenuation of Airplane Noise During Takeoff and Landing”, (AIR-1751), Society of Automotive Engineers, 1981). Likewise, however, these devices are not devices for supporting the pilot in performing a flight that takes noise conditions on the ground into account and reduces noise.